Automatic voltage regulating apparatus for ac generator with antihunt means

ABSTRACT

An automatic voltage regulating apparatus for an AC generator, comprising an instantaneous voltage change detecting means with a blind sector which acts to impart its output to the automatic voltage regulator only when the instantaneous voltage change thereof exceeds a predetermined value, provided in parallel with a voltage deviation detecting loop in an automatic voltage regulator for said generator, whereby when the instantaneous voltage change of the generator becomes more than a predetermined value, a transient response characteristic of said voltage regulator is caused to increase only for a predetermined period in response to said voltage change.

United States Patent Inventors Masaomi Nagae;

Sumio Yokokawa, both of Kawasaki-shi,

Japan Appl. No. 224 Filed Jan. 2, 1970 Patented Nov. 16, 1971 Assignee Fuji Denkl Sum Kabushiki Kaisha Kawasaki-slit, Kanagavva-ken, Japan Priority Jan. 9, I969 Japan 44/1844 AUTOMATIC VOLTAGE REGULATING APPARATUS FOR AC GENERATOR WITH References Cited- UNITED STATES PATENTS 2,913,656 H959 Bliss 322/19 X 3,474,323 i0/i969 Kilgore 6! al. 322/19 Primary Examiner-Oris L. Rader Assistant Examiner-4i. Huberfeld Attorney-Holman 8c Stern ABSTRACT: An automatic voltage regulating apparatus for an AC generator, comprising an instantaneous voltage change detecting means with a blind sector which acts to impart its output to the automatic voltage regulator only when the instantaneous voltage change thereof exceeds a predetermined QELLZ E value, provided in parallel with a voltage deviation detecting raw loop in an automatic voltage regulator for said generator,

U.S.Cl 322/19, whereby when the instantaneous voltage change of the 322/20, 322/24, 322/28, 322/36, 322159.318/624 generator becomes more than a predetennined value, a

lnt.Cl. 02p 9/14 transient response characteristic of said voltage regulator is Fieldotsearcli 322/19, 20, caused to increase only for a predetermined period in 24, 25, 28, 36, 59; 318/2044] response to said voltage change.

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sum 2 OF 2 FIG.4 FIG-5 INVENTORS 07. MAG/FE -5- YOK. my own A rm 4 NEKS BACKGROUND OF THE INVENTION The present invention relates to an automatic voltage regulating apparatus comprising an automatic voltage regulator (hereinafter referred to as AVR) for an AC generator.

For the purpose of improving a transient response characteristic of excitation system of an AC generator, it has been well known to detect voltage of an excitor of said excitation system thereby to compensate a time constant of said excitor, but according to this method, a special device is required for detecting the voltage of said excitor, particularly in the case of a brushless AC generator.

Furthermore, a method of imparting PID (Proportional, Integral, Differential) characteristic to the AVR in order to improve a transient response characteristic of any excitation system has been well known, but according to this method a ripple of the normal detected input is enlarged because of its differential characteristic, thus causing fluctuation in the response characteristic at a normal operation.

Generally, an object of improving the transient response characteristic of an excitation system of an AC generator is to increase stability with increase of abnormal change of bus for voltage due to breakdown of the power system and to suppress voltage increase at the time of cutting off a load within 20 percent to 30 percent in the case where the generator is connected in parallel with the power system, and to suppress abnormal drop of the generator terminal voltage due to the rush current at the time of putting on a load and voltage buildup at the time of cutting off a load in the case where the generator is singly operated.

Accordingly, in order to deal with the voltage fluctuation at the normal condition, the characteristic of the AVR is sufficient to have the PI characteristic, but at the time of putting on and cutting off a load, the AVR with the Pl characteristic brings about drawbacks such that the voltage drop and the buildup factor of the voltage are too large, and also the voltage recovery time becomes longer.

SUMMARY OF THE INVENTION An abject of the present invention is to improve the transient response characteristic of the excitation system for the AC generator without compensating for the time constant of the excitor directly or indirectly.

Another object of the present invention is to make it possible to employ an AVR having only PI characteristic as the excitation system for the AC generator.

A further object of the present invention is to minimize the voltage fluctuation and to shorten the voltage recovery time by adding a differentialcharacteristic to the AVR at the time of abnormal voltage fluctuation.

The foregoing object and the other objects as well as function of the invention have been attained by an automatic voltage regulating apparatus for AC generator, which comprises an instantaneous voltage change detecting means with a blind sector, said means being provided in parallel with a voltage deviation detecting loop in an automatic voltage regulator for said AC generator and comprising a device adapted to increase a transient response characteristic of output of said automatic voltage regulator only for a predetermined period in response to an instantaneous voltage change of said generator when said voltage change becomes more than a predetermined value.

The present invention will be more apparent and more readily understandable by the following description and the appended claims when read in conjunction with the accompanying drawings, in which same or equivalent elements are designated by the same numerals and characters.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is'a block diagram of one embodiment of the present invention;

FIG. 2 is a block diagram showing transmitting function of the voltage loop in the apparatus shown in FIG. 1;

FIG. 3 is a connection diagram of a partial circuit in the apparatus shown in FIG. 1;

FIGS. 4 through 6 are voltage, current-time characteristic diagrams for describing operation of the apparatus shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION The organization and function of the embodiment of the present invention will be described in conjunction with the accompanied drawings. I

Referring to FIG. I, an AC synchronous generator 3 which is parallelly operated with a power system I through a main transformer 2 is equipped with a rotary unit of excitation system consisting of a generator field winding 5, a bridge rectifier 6 and an AC excitor 7. An excitation winding 8 of the AC excitor 7 is controlled by an AVR l6 and a main amplifier 17. AVR 16, as aforementioned, comprises an automatic voltage regulator of any well-known conventional construction, one such construction contemplating the use of a conventional proportion and integration adjusting amplifier. Likewise, amplifier 17 is of any conventional known construction. The power source voltage of the AVR l6 and main amplifier I7 is supplied by the generator bus bar through a transformer 9 for excitation power source. The apparatus comprises a current transformer (CT) 10 for detecting output current of the generator 3, a potential transformer (PT) I l for detecting output voltage of the generator 3, a voltage deviation detecting unit 12 for detecting deviation between a set voltage and a real voltage obtained from the potential transformer 11, and a power factor deviation detecting unit I3 for detecting deviation between a set power factor and a real power factor, outputs of said detecting units l2, 13 being supplied to the AVR in the known manner. Unit 12 may be of any conventional design similar to that of a difference amplifier, for example. Unit 13 is also contemplated to comprise any known construction achieving the standard described function.

In the apparatus shown in FIG. 1, and as mentioned, the members designated by numerals I through 13 and their interconnections are all well known, but the apparatus comprises, additionally, a voltage change detecting unit 14 and a blind sector setting unit 15 provided by the present invention.

In the normal condition, the excitation system operates through a circuit of 10, 11 l2, 13 -16 17 and a favorable stabilized voltage regulation is taken place by the AVR 16 having the Pl characteristic. The block diagram showing transmitting function of voltage loop in the normal condition mentioned above is shown in FIG. 2. In FIG. 2, q, is a voltage setting value, 2, is a generator terminal voltage, K, is a proportional gain of the AVR 16, T, is an integration time of the AVR 16, T is a time constant of the excitor, and T is an open-circuit time constant of the generator circuit.

In case an abnormal buildup or abnormal drop of the voltage occurs, its differential quantity is fonned at the voltage change detecting unit 14, and is superimposed on an input signal of the AVR 16 through the blind sector setting unit 15.

FIG. 3 designates a circuit example of the voltage change detecting unit 14 and the blind sector setting unit 15 in F 1G. I, in which a voltage E, proportional to the generator terminal voltage is subjected to full wave rectification in a rectifier S,, the thus rectified voltage is obtained at a resistor r,,, and said rectified voltage is caused to pass a differential circuit consisting of a capacitor C and resistor r,, whereby any changed component of the voltage is detected and this changed component is supplied to a blind sector circuit consisting of a resistor r and Zener diodes Z and 2 which are reversely connected in series.

When let it be assumed that current flowing in the capacitor C, terminal voltage of the resistor r,, Zener voltage, and blind sector output voltage are respectively represented by i E,,, E and E, variations of the values i E E and E with respect to time in the case when the generator terminal voltage E, changes stepwise by AE, are shown in FIGS. 4 and 5. HO. 4 shows a variation of the above-mentioned values at the time of rapid decrease of the voltage E, and FIG. 5 shows it at the time of rapid increase of the voltage E,.

Now, if r r, r is established, the step change AB of the generator terminal voltage E, becomes as follows.

and the output voltage E of the blind sector setting unit becomes at the time of the rapid decrease of the voltage and at the time of the rapid increase of the voltage.

-l. aimlwielfl g l Accordingly, in case the output voltage E of the blind sector is supplied to the input of the AVR with a polarity as shown in the drawing, an increasing signal can be obtained at the time of the rapid decrease of the voltage and a decreasing signal can be obtained at the time of the rapid increase of the voltage. The blind sector width E, is preferably set to a value within 5 percent with respect to 100 percent of the generator voltage. By the provision of an instantaneous voltage change detecting means with the blind sector as described in the foregoing passage, the output voltage E of the blind sector is multiplied by K times and is superimposed to the output of the AVR which changes in accordance with the Pl characteristic as shown in FIG. 2 only for a limited period of generation of the output voltage E of the blind sector, when width of the variation of the generator terminal voltage becomes more than a predetermined value due to on or off of a load. In case the value of the step change of the voltage is less than the predetermined value, the AVR 16 operates stably as the Pl regulator.

FIG. 6 shows the output of the AVR for E, in connection with open loop, in which P represents the output of the AVR due to the proportional gain corresponding to the output of the voltage deviation detecting circuit 12 at the normal time, and l represents the output of the AVR due to an integration characteristic.

In the embodiment of the present invention, 100 percent output voltage of the voltage change detecting unit (reference numerals l4, 15 in FIG. 1) is preferably selected to approximately 10 times of the percent output voltage of the voltage deviation detecting unit (reference numeral 12 in FIG. 1) for the same change of the terminal voltage of the generator.

As described in the foregoing, in case the voltage change occurs, it is possible to remarkably improve the restoring characteristic of the terminal voltage of the generator by imparting a forced input which disregards the stabilized control of the excitation system to the field of the excitor for a predetermined period being responsive to said voltage change.

It is needless to say that present invention is useful in improving the similar transient response characteristic not only to the brushless AC generator butalso to general AVR apparatus.

We claim:

1. An automatic voltage regulating apparatus for AC generator, which comprises an AC generator, an automatic voltage regulator for adjusting field system of said AC generator, a voltage deviation detecting unit for detecting a deviation of output voltage of said AC generator from a set voltage, a first means for imparting an output of said detecting unit to an input of said automatic voltage regulator, a second means for detecting an instantaneous value of the terminal voltage of said generator, a third means for differentiating the output voltage of said second means, a fourth means for generating an output when the output voltage of said third means becomes more than a predetermme value in each of positive and negative polarities, and a fifth means for applying the output of said fourth means to an input of said automatic voltage regulator.

2. ln an automatic voltage regulating apparatus for AC generator, which comprises an excitor of said AC generator and an automatic voltage regulator for controlling excitation of said excitor in response to output states such as output voltage, output current and output power factor of said AC generator; the improvement comprising additionally a voltage change detecting unit adapted to'detect the output voltage change of said AC generator and a blind sector setting unit connected at its input with the output side of said detecting unit and adapted to produce an output only when instantaneous voltage change detected by said detecting unit exceeds a predetermined value, the output side of said blind sector setting unit being connected at its output side with the input side of said automatic voltage regulator, thereby to increase a transient response characteristic of output of said automatic voltage regulator only for a period in response to an instantaneous voltage change of said generator when said voltage change becomes more than a predetermined value. 

1. An automatic voltage regulating apparatus for AC generator, which comprises an AC generator, an automatic voltage regulator for adjusting field system of said AC generator, a voltage deviation detecting unit for detecting a deviation of output voltage of said AC generator from a set voltage, a first means for imparting an output of said detecting unit to an input of said automatic voltage regulator, a second means for detecting an instantaneous value of the terminal voltage of said generator, a third means for differentiating the output voltage of said second means, a fourth means for generating an output when the output voltage of said third means becomes more than a predetermined value in each of positive and negative polarities, and a fifth means for applying the output of said fourth means to an input of said automatic voltage regulator.
 2. In an automatic voltage regulating apparatus for AC generator, which comprises an excitor of said AC generator and an automatic voltage regulator for controlling excitation of said excitor in response to output states such as output voltage, output current and output power factor of said AC generator; the improvement comprising additionally a voltage change detecting unit adapted to detect the output voltage change of said AC generator and a blind sector setting unit connected at its input with the output side of said detecting unit and adapted to produce an output only when instantaneous voltage change detected by said detecting unit exceeds a predetermined value, the output side of said blind sector setting unit being connected at its output side with the input side of said automatic voltage regulator, thereby to increase a transient response characteristic of output of said automatic voltage regulator only for a period in response to an instantaneous voltage change of said generator when said voltage change becomes more than a predetermined value. 